Perfluorinated imines and amines



United States Patent Oflice 3,461,162 PERFLUORINATED IMINES AND AMINESRobert J. Koshar, Lincoln Township, Washington County, and Donald R.Husted, St. Paul, Minn., assignors to Minnesota Mining and ManufacturingCompany, St.

Paul, Minn., a corporation of Delaware No Drawing. Continuation-impartof application Ser. No.

19,111, Mar. 31, 1960. This application Mar. 30, 1961,

Ser. No. 99,632

Int. Cl. C07c 119/00, 129/08, 17/10 U.S. Cl. 260-564 4 Claims Thisapplication is a continuation-in-part of our copending application Ser.No. 19,111, filed Mar. 31, 1960 and now U.S. Patent No. 3,354,216.

This invention relates to highly fluorinated compounds of carbon andnitrogen and particularly to certain very highly fluorinated oxidizingagents containing fluorine, nitrogen and carbon, and the process for thepreparation thereof.

It is well known that fluorine is the most electronegative element andtherefore is an oxidizing agent with very high potential. However,fluorine is a very low boiling and highly corrosive gas requiring ratherspecial techniques in its manipulations, which limits the extent towhich its high oxidizing potential could otherwise be utilized for usewhere high output is required. Among such possible uses are a number ofindustrial processes where high oxidizing potential can extend the rangeof application, increase rate of output and the like. Many industrialrequirements have heretofore been met in a more or less satisfactory wayusing less powerful and more readily handled oxidizing agents. Bleachingof wood pulp, fabrics, flour and such materials may be mentioned amongsuch uses. However, more active oxidizing agents would be advantageousin such industrial uses if readily handled, permitting shorter processtime, use of lower concentration, etc. Another field in which very highoxidation potentials are particularly desirable is in the field ofreaction-type propellants where extreme releases of energy are necessaryto achieve high specific impulses. For such purposes the availability ofrelatively safely handled material possessing even a substantialfraction of the oxidizing capacity of fluorine but still at a highpotential would be very desirable in formulating solid propellants, orfor use as oxidizers in liquid propellant systems.

It is known that the oxidizing potential of fluorine is retained to aconsiderable extent in -NF and =NF radicals but methods of synthesis ofcompounds containing such radicals are very severely limited and theintroduction of a plurality of such radicals into a molecule hasheretofore been extremely difiicult.

It is an object of this invention to provide fluorinecontainingcompositions having substantial oxidizing capacity. A further object isto provide highly fluorinated derivatives of guanidine containingfluorine in oxidizing configurations. A still further object is toprovide oxidants having high oxidizing capacity at a high potential.Another object of the invention is to provide a process for producingthe compositions of the invention. Other objects will become evidenthereinafter.

In accordance with the above and other objects of this invention, it hasnow been found that compositions containing a plurality of -NF and -=NFgroups are formed by direct fluorination of compounds containing atleast one carbon atom bonded to three nitrogen atoms. One type of thesecompounds is believed to be represented by the formula:

3,461,162 Patented Aug. 12, 1969 wherein n is a large number from about50 to 1000 or greater. These compounds are described by A. E. A. Wernerin the Scientific Proceedings of the Royal Dublin Society, volume 24,page 199 if. for 1947 and the above structure is suggested as well asthe less probable isomeric structure represented by the formula:

NH NH No attempt is there made to name these polymeric compounds. Itwill be noted that the recurring units of the first structure arecarbonylguanidylene radicals which are divalent. The termination of thechains is probably as shown. It will be understood that we are notlimited to the structures postulated in using these names but referspecifically to substances formed by interaction of guanidine witheither urea or urethane. It has now been found that a significantamount, up to about equal parts of ammeline is formed by the Wernerprocess for preparing polycarbonylguanidylene and is present in thereaction product since it is not separated by Werners purificationprocedures. As pointed out hereinbelow, the products of the inventionare also produced by the fluorination of ammeline alone, as well as bythe fluorination of the mixture produced by the Werner process.

Other compounds useful for the purposes of the invention are the acycliccompounds guanidine hydrochloride, dicyanamidazide, biguanide,triguanide and the hydrofluorides thereof; the monocyclic compoundsmelamine, ammeline and ammelide and the polycyclic compound potassiumcyamelurate. It will be seen that all of these compounds include intheir structure the characteristic structural grouping of at least onecarbon atom attached to three nitrogen atoms.

It has been disclosed heretofore that guanidine itself, as well as urea,hydrazine, biuret and the like compounds when subjected to directfluorination either are extensively cleaved and produce substantiallyonly very low-boiling products or are very incompletely fluorinated toproduce solids having no appreciable oxidizing capacity. However, wehave found that the highly useful compounds of this invention can beobtained by the techniques described here- 1n.

The fluorination of the starting materials set forth above produceshighly fluorinated, shock-sensitive oxidant compositions which containsubstantially only carbon, nitrogen and fluorine in acyclicconfiguration, containing at least two fluorinated nitrogen atoms, andhaving a ratio of nitrogenzcarbon atoms ranging from 1:1 to 3:1; andcharacterized by containing more than about 25% of fluorine and havingoxidizing capacity equal to at least about 5 to 50 milliequivalents ofiodine per gram.

These compounds have the formula:

wherein R is a member of the group consisting of =NF, NF NFCF N'FCF NFNFCF==NF, -NFCF(NF IIIF -NFONF,

=NCF =NCF NF =NCF=NF and =NCF(NF radicals; Y is a linking radical of thegroup consisting of It will be noted that in the third, fourth,fifteenth and sixteenth formulas the carbon-nitrogen double bond isintact although empirically the compound is named as perfluorinated. Thesignificance of the content of fluorine to nitrogen bonds is that suchbonds possess energy and are powerful oxidants. It was not heretoforebelieved that direct fluorination reactions resulted in useful andstable products with high contents of nitrogen to fluorine bonds.

Thus, it is found that direct fluorination using elemental fluorinereplaces substantially all of the hydrogen atoms contained in thesesource materials by fluorine atoms, whether these compounds are presentundiluted or as a suspension in a suitable liquid inert to fluorine. Itappears from what can be determined from the stoichiometry of thereaction and the analytical values obtained on the products that thereaction not only replaces substantially all of the hydrogen atoms byfluorine atoms but that in addition greater or lesser amounts offluorine combine with the source materials, e. g.poly(carbonylguanidylene) by addition to the carbon-nitrogen doublebonds which are present. Addition of fluorine also causes some cleavageof the C-N skeletal chain of the polymeric and cyclic substances. Theresultant products, which vary over certain ranges of fluorine content,contain a number of compounds which can be isolated by the methodsdescribed herein. There is reason to believe that not all of the doublebonds present add fluorine and fluorinolysis would be expected to resultin complete decomposition of the source materials to produce CF COF andHF. Surprisingly, the reaction stops well short of complete degradationto produce white to yellowish, liquid and amorphous materials, which maybe non-crystalline to sticky solids, greases, or mobile liquids whichmay be low-boiling in which the fluorine content on analysis may varyfrom about 25 percent to about 75 percent by weight and the oxidizingcapacity determined as described hereinbelow is from about 5 to 50 ormore milliequivalents of iodine per gram. Oxidizing capacity isdetermined using excess potassium iodide in aqueous acetonitrile oracetic acid followed by titration with standard solutions of sodiumthiosulfate. The products have vapor pressures up to about 100 mm. of Hgat -7 8 C. to less than 50 mm. of Hg at 25 C., and are considered tocomprise both volatile and nonvolatile substances. The low vaporpressure amorphous compositions of the invention are shock-sensitive,but are usually not so sensitive that they cannot be handledconveniently.

There is a wide range of sensitivity among compounds which are sensitiveto shock or impact. Many such compounds, although sensitive, can be usedsafely; commercial explosives fall in this class. A widely-used methodof evaluating the degree of sensitivity consists of dropping a weight(frequently a two kilogram weight is employed) onto a small sample ofthe compound and determining the height of drop at which detonationoccurs. The product of the weight used and height of drop, expressed inkg. cm., is then a measure of the sensitivity and this product isgreater for the less sensitive materials.

The materials herein described have sensitivities, expressed as kg. cm.,which place them outside the range of the most sensitive materials. Theycan accordingly be manipulated using suitable precautions, and thus theyare different from many known materials having high oxidative capacitywhich cannot safely be manipulated. It is, of course, only normallyprudent to exercise considerable care under all circumstances since,when detonated, materials of such high energy content produce veryviolent explosions and in fact are so powerful as oxidizing agents thatthey can ignite many common organic substances. In no case shouldquantities over about 10 milligrams be detonated for testing.

The amorphous compositions of the invention are thus seen to beamorphous, shock-sensitive compositions which contain carbon, nitrogenand fluorine, and which have an oxidizing capacity of from about 5 to 50or more milliequivalents of iodine per gram. They appear to consist ofmixtures of similar compounds with somewhat different physicalproperties, which are separated from each other with difliculty. Theycontain substantially no residual hydrogen in the molecule, and, whenthey are solids, are insoluble in the common organic solvents, but canbe dispersed in a variety of inert solvents and are generally soluble tosome extent in fluorocarbon solvents. The liquid products are soluble insuch solvents as methylene chloride, fluorotrichloromethane and thelike. The solid materials do not melt, but decompose on heating; certainof the liquids may be distilled with great caution under highly reducedpressure; others may be distilled readily at atmospheric pressure. Whenmixed with substances which can be oxidized, such as an organic polymer,and ignited as by means of a squib, they burn with intense heat and theformation of large volumes of gases. When treated with water, or exposedto moisture, these fluorinated compounds may hydrolyze to a greater orless extent with a lowering or loss of their oxidizing power.

The more volatile products, which are often normally gaseous, arerelatively shock insensitive in the pure state and consist of carbon,nitrogen and fluorine and have oxidizing capacities of from about 5 toupwards of 50 milliequivalents of iodine per gram. They are somewhatseparable by distillation and more completely by vapor phasechromatography employing a fluorochemical stationary phase as more fullydescribed hereinafter. They are generally relatively soluble (even whengases) in fluorocarbon solvents such as perfluoro octane and higherboiling products of the reaction and are much less soluble inhydrocarbons. Their reactivity is variable. Those which possess a C=Nbond are readily hydrolyzed by dilute (e.g. 5l0%) aqueous alkali atordinary temperatures whereas the saturated compounds are relativelystable to this reagent under the same conditions.

Broadly speaking, the process of the invention is carried out bytreating the carbonylguanidylene polymers and other source materialswith elemental fluorine. For best results, the starting material shouldbe substantially anhydrous, to avoid destruction of the =NF or -NFgroups after their formation. The process can be carried out at atemperature in the range of about l to +40 C. or even somewhat higher.Reaction takesplace very slowly at 100 C. and is markedly increased byraising the temperature to -75 C. or higher. The fluorine isconveniently introduced under slight positive pressure, or if closedvessels are used, by employing diluents and proper precautions,pressures up to 100 p.s.i. can be used. Preferably, the fluorine isdiluted with nitrogen or other inert gas such as argon or helium, or aFreon, such as dichlorodifluoromethane and the like, to give about 0.1to 60 percent of fluorine in the gas stream. Too high a concentration isindicated by burning of the starting materials and this can be avoidedby reduction of the fluorine concentration and/ or lowering the reactiontemperatures, however, undiluted fluorine can be used, using greatcaution and slow addition when working with solid, finely powderedundiluted reactants. Residual fluorine should always be flushed out ofthe reactants and the apparatus, using dry nitrogen or the like, toavoid unpleasant and toxic exposure to fluorine as well as untowardeffects owing to the strong oxidizing power of this substance. Theapparatus used is preferably constructed from monel metal or copper. Thesolid, in finely divided form, is placed in a suitable container, suchas a boat, which may be of stainless steel or copper or spread on asheet or plate, and is then contacted with fluorine for a period rangingfrom about 10 minutes to about 6 hours. Longer times are usually usedwith more highly diluted fluorine and for large samples. Generallyspeaking, once the process has gone to completion, no further fluorinereacts, so that continuation of the flow of fluorine is not deleterious;but excessive exposure to fluorine, of the order of 10 hours or morewhen highly concentrated fluorine is used, should be avoided to suppressthe possibility of extensive fluorinolysis. Preferably, the reactionmixture is maintained at a temperature in the range of about 20 to +25C. and the fluorination process is continued for about hours or longerfor larger samples. The time depends on the fluorine flow rate as wellas sample size. When convenient, lower temperatures can be used and itis preferred to use temperatures not in excess of about 25 C. Ifdesired, an inert liquid suspending medium can be used to suspend thefinely divided reactant, and the fluorine gas with or without a diluentgas is then bubbled through the suspension. Thus, for example,fluorine-inert liquids such as perfluorinated hydrocarbons, e.g.perfluorooctanes, perfluorohexanes, and the like; perfluorocyclohexanes;perfluorinated cyclic ethers such as perfluorobutylfuran; perfluorinatedtertiary amines such as trisperfluoro-n-butylamine; and the like.Commercially obtainable fluorocarbons may contain an amount of materialwhich is not inert toward fluorine, and in such cases, fluorine gas ispassed through the selected fluorocarbon liquid for a time in smallamounts just suflicient to render it substantially completely inerttoward fluorine. When an inert lfquid diluent is employed in the processof the invention, the hyperfluorinated reaction product generallydissolves in the diluent. The reactant may also be mixed with a finelydivided solid material which is inert to fluorine under the conditionsof fluorination; such materials include sodium fluoride, calciumfluoride and graphite. The fluorine gas is then passed over or throughthe solid mixture.

In the procedure where no solvent is used, the product of the process isrecovered for use by removal of the excess of fluorine gas andseparation from any highly volatile fluorinated cleavage products suchas CR NF etc. which may be present. Where solvent is employed, anyinsoluble material is removed by filtration and the product is recoveredby evaporation of the solvent, preferably under reduced pressure.

The following examples will more specifically illustrate the fluorinatedoxidant compounds of the invention and the process for theirpreparation.

8 Example 1 This example illustrates the process of the invention inwhich no diluent is employed. This process is referred to as static bedfluorination.

The reaction product of guanidine and urethane is prepared as desrcibedby A. E. A. Werner in Scientific Proceedings of the Royal DublinSociety, vol. 24, p. 199 (1947) and has an inherent viscosity of 0.162in trifluoroacetic acid. It has now been found to be a mixture of aboutequal parts of poly(carbonylguanidylene) and ammeline.

In a stainless steel boat is placed a sample of 205 mgm. of the abovedry mixture and the boat is placed in a 1 inch by 14 inch nickel tubehaving a polytetrafluoroethylene rupture disc at one end and arranged bymeans of a side arm, so that gases can be introduced at one end andremoved at the other. A stream of dry prepurified nitrogen is forcedthrough the tube containing the sample at about 130 ml. per minute todisplace air since fluorine subsequently introduced may produceexplosives with oxygen. Fluorine (commercially available, percent pure)is introduced into the nitrogen stream (using monel metal fittings) togive a concentration of 8.9 percent fluorine by volume and the stream ofnitrogen and fluorine is passed over the mixture at about 20 C. for 3.66hours. The volatile and entrained fluorination products are removed atthe far end of the tube, passed through sodium fluoride in an iron tubeheated to about 90 to 105 C. (to remove hydrogen fluoride) and anyresidual materials are condensed in a borosilicate glass trap cooled ina liquid air bath. At the end of 3.66 hours the flow of fluoride isstopped and that of nitrogen continued for about 30 minutes to flushthrough residual amounts of fluorine. The stainless steel boat containsa yellow amorphous solid. Decomposition by the procedure reported bySenkowski, Wolliski and Shafer in Analytical Chemistry, vol. 31, pp.1574-1576 (1959) followed by titration with standard thorium nitratesolution using sodium Alizarin Red S as indicator shows 34.7 percent byweight of fluorine. Reaction of a sample with excess potassium iodide inacetonitrile followed by titration using standard iodmetric proceduresshows that the amorphous yellow hyperfluorinated material has anoxidizing capacity of 14.1 milliequivalents (meq.) of iodine per gram.For this product the impact sensitivity was less than kg. cm. Theminimum value is not usually determined. The fluid and liquid productsformed in this reaction and entrained by the gas stream is notconveniently recovered on this scale although a trace of liquid is foundin the liquid-air trap.

In other runs using 219 and 314 mgm. amounts of material with from 5.7to 3.6 percent by volume of fluorine and for 1.87 and 4.58 hours at 22and 70 C., all respectively, other mixtures of solid products areobtained having oxidizing capacities of 14.9 and 7.8 meq. iodine pergram respectievly.

Example 2 The procedure of Example 1 is repeated employing 1101 mgm. ofthe same starting material. The fluorination vessel is a copper U-tubemaintained at about 70 C. by means of solid carbon dioxide through whicha stream of 8.57 percent fluorine concentration is passed for 5 hours(total of 0.12 mole of F at the end of which time the reactor is allowedto warm up to room temperatures and the nitrogen stream is continued for3 to 5 hours to flush through fluorine and entrain as much as possibleof the more volatile products. The gases pass through a sodium fluoridescrubber as above. On this larger scale an appreciable amount ofmaterial is collected in the liquid air trap as well as a substantialamount of yellowish solid remaining in the reactor. The solid materialcontain 32.4 percent fluorine by weight and has an oxidizing potentialof 7.4 meq. iodine per gram.

The liquid in the trap designated as A is separated into fractions byconnecting the trap (kept cold in liquid air) to a line passing seriallythrough two receivers herein designated B and C. The first receiver, B,is cooled to 78 C. by a carbon dioxide-trichloroethylene bath and thesecond receiver, C, is cooled in liquid air. The liquid air bathsurrounding the original trap, A, is removed and the contents permittedto vaporize as the temperatures gradually rise to ambient temperature. Aliquid residue remains in the original trap. The less volatile portionof the vapors is condensed in receiver B, the more volatile material inreceiver C. The product in C contains fragments such as CF NF and CO andis usually discarded. Both compositions in B and the original trap, A,are mixtures, part of the more volatile components being retained intrap A as a result of solubility in the less volatile constituents ofthat composition. The product distribution in trap A and B can varyconsiderably by varying the time in which trap A is maintained at theambient room temperature. On a run using twice the amount of startingmaterial, the residue remaining in trap A was found to contain a liquidresidue not evaporated at 46 mm. Hg and 25 C. which was found to besensitive to shock, heat and even to the light contact between a glasspipette containing some of the material and the walls of the container.The contents of receiver B is analyzed by vapor phase chromatographyusing a polytrifiuoroethylene oil as the continuous phase, nuclearmagnetic resonance and infrared absorption spectroscopy and is found toconsist of a mixture of about 75 percent of a mixture of low molecularweight cleavage products, e.g. CF NF (CF NF, COF NF and SiF and about 25percent of a mixture of other compounds, including appreciable amountsof CF (NF and a small amount of CF(NF By the same method, the contentsof trap A is found to consist of about 25 percent of a mixture of lowmolecular weight cleavage products, e.g. trifluoromethyl-difluoroamineetc. and about 75 percent of other compounds including as the majorcomponents, CF (NF and CF(NF In each case, further separation intofractions can be accomplished by vapor phase chromatography and thecompounds present in significant amount can be isolated. Compounds whichwere initially isolated include his difluoroamino difluorometh ane CF(NF and tris(difiuoroamino)fluoromethane (CF(NF The contents of tray Babove is further characterized by the nuclear magnetic resonanceshielding values (employing CFCl as internal standard as described byFilipovich et al., Journal of Physical Chemistry, vol. 63, pp. 761-762(1959); the values defined by these authors are here given simply asvalues) and shows the following important peaks (all such values areapproximate to about 1%):

The intensities of the peaks due to CF (NF and CF(NF are inapproximately the theoretical ratios as hereinafter described.

The residue in trap A is evidently less volatile. The infraredabsorption spectrum shows a high ratio of NF bonds in the lO1l micronregion to CF bonds (7.5 to 8.5 micron region) and some unsaturation (4.3to 6.4 micron region).

Nuclear magnetic resonance shielding values permit the furthercharacterization of this mixture from the following values:

47.2, 42.4peaks of about equal area due to F of NF in perfluoroguanidine24.3qb-F f NF in CF(NF 10 20.0F of NF in or asm 19.0-and shoulder atless negative value due to F of =NF in perfluoroguanidine +67(and +69)two very weak unrecognized peaks of about equal area probably due to Fin CR; groups Of CF2 in CF3NF2 +85.7(and shoulder to higher values)unassigned C-F and N-F peaks l00CFCl reference of CF2 in CF2(NF2)2 Thepeaks at 24.3 and 19.0 are rather broad and presumably obscure NF peakswhich are correlated with the small amounts of material responsible forthe unassigned peaks at about +67 and +85.7. Vapor phase chromatographyshows the presence of about 1 percent of at least one more compound thancan be recognized unequivocally and there is a suggestion in the nuclearmagnetic resonance curve of several very small peaks which are scarcelydistinguishable from background noise.

In order to prepare CF (NF and CF(NF in substantially pure form thecontents of trap A and receiver B from a series of several runs arepooled and fractionated to remove materials boiling below about 40 C.which includes virtually all the low molecular weight cleavage products,eg CF NF NF and CF.,. The residue can then be further rectified toprovide a fraction having a vapor pressure at 75 of equal to or lessthan 40 mm. and a vapor pressure at +25 of greater than 25 mm. Thismixture, having an estimated boiling range of 30 to +25, consistslargely of CF (NF CF(NF and other compounds of high NF content. It isfound that CF (NF and CF(NF are accompanied by a considerable number offiuorinated compounds in varying amounts.

In this manner a sample is subjected to vapor phase chromatographyemploying the abovementioned fluorochemical stationary phase toconcentrate the substances (including CF (NF and CF (NF having high NFbond content and a single fraction is obtained corresponding to CF(NFThis material is found by infrared spectral analysis to contain anunsaturated component which had only NF and no CF absorption and whichis confirmed by nuclear magnetic resonance shielding values to beprefiuoroguanidine. The peaks are:

47.5. 42.5-Peaks of about equal intensity due to F in the NF groups ofperfluoroguanidine 23.lPeak due to F of NF groups CF(NF l9-Shoulder on23.1 peak due to F of the =NF group in perfluoroguanidine of much lowerintensity than the above two peaks.

+138F in CF group of CF(NF Planimetrically the areas of the four peaks(the shoulder at 19 being included in the 23 peak) are respectivelyabout 0.5 :0.5:6.1:l. It is seen that the shoulder contributes only asmall fraction, ca. 0.2, to the area of the larger peak and that thesubstance in question must be perfluoroguanidine since there are nounassigned peaks even of very low intensity.

As a result of the above vapor phase chromatography a fractioncontaining a considerable amount of CF (NF is also obtained. Theinfrared absorption spectrum shows weak intensity peaks at 4.38, 4.58and 5.85 microns which indicate probable unsaturation. Nuclear magneticresonance shows the presence of a compound, perfluoroformamidine, havingthree types of fluorine bonds (42.3, +83.5 and very weak at about +21)as well as some other compounds.

In order to separate CF (NF and CF(NF in pure condition with the leastelfort, although at the expense of some of these other substances, thegases containing CF (NF and CF(NF are scrubbed with aqueous sodiumhydroxide to by weight) at about 25 C. and dried over CaSO before vaporphase chromatography. This results in destruction of the more reactiveconcomitants, particularly perfluoroformamidine and perfiuoroguanidine,and simplifies the separation. Substantially the same result is achievedby exposing the gases to ultraviolet irradiation of wave lengths aboveabout 2500 A. At shorter wave lengths CF (NF and CF(NF also show atendency to decompose.

For preparative purposes a Beckman Megachrom 12 foot GLC column ispacked with tetrameric polytrifluorochloroethylene absorbed on speciallyprepared diatomaceous earth. The column is held at 25 C., the block at90 C. The sample is introduced and moved in a stream of helium under apressure of 6 lbs. per square inch at the inlet and 1 lb. per squareinch at the outlet. The samples (previously scrubbed with aqueous sodiumhydroxide) are stored in and injected into the system from a barricadedsteel cylinder. The compound, CF (NF is eluted in 9.5 minutes (peak) andCF(NF in 24.5 minutes (peak).

Bis(difluoroamino)difluoromethane (CF (NF is colorless 'both as a liquidand as a gas and is found to be relatively shock insensitive. Its vaporpressure in mm. (P), when T is the absolute temperature in K., isapproximately expressed by the equation:

The boiling point at atmospheric pressure is thus about 32 C. and theheat of vaporization is about 5.3 kcal./ mole. Its density at 25 C. wasfound to be 1.901 g./cc. (under pressure). The infrared absorptionspectrogram shows a strong double peak at 7.7 to 8.0 micronscorresponding to the C--F bonds and two strong peaks at about 10.4 and11.0 microns corresponding to the NF;; groups.

Analysis.-Calculated for CF N 7.8% C; 74.0% F; 18.2% N; mol. wt. 154.Found: 8.1% C; 73.1% F; 17.9% N; mol. wt. 150.

Bis(difluoroamino)difluoromethane possesses nuclear magnetic resonanceshielding values (using chlorotrifluoromethane as internal reference) at19.0 (corresponding to the four equivalent nitrogen to fluorine bonds)and at +112.9 (corresponding to the two equivalent carbon to fluorinebonds). It has long been known that nuclear magnetic resonance (oftenabbreviated as n.m.r.) can serve as a means for group analysis, i.e.functional groups involving hydrogen, as well as for fluorine. Anexample is provided by Gutowsky, Analytical Applications of NuclearMagnetic Resonance in Berl, Physical Methods of Chemical Analysis,volume 3, pp. 303381, Academic Press, N.Y. (1956). While the errors indeterminations of the intensities may be fairly high (for a discussionsee, R. B. Williams, Annals of the New York Academy of Sciences, vol. 7,pages 890-899 (1958)), a large part of the error is smoothed over inrelatively simple molecules such as low boiling liquids and normallygaseous materials of the invention where the relationships of theintensities must be as ratios of small whole numbers and wherefurthermore only a limited number of types of groups are inolved. For CF(NF it is found that the ratio of the intensities of the peaks at -l9.0and +112.9, respectively, are close to 2:1. This is in agreement withthe required relationship of intensities of 4:2 based upon the presencein the molecule for four nitrogen to fluorine and two carbon to fluorinebonds. The intensities of the respective peaks are readily measured onthe plotted curves as the integrals of the peak and may be determined byany of the usual methods for integration, e.g. by planimetry,graphically or by weighing of the cut-out curve. It is equally possibleto proceed from the n.m.r. data to determine the structure. The presenceof only two types of fluorine bonds indicates a simple structure. Theratio of 12 2:1 of FN to FC bonds and the fact that each N requires twofluorine atom also leads to the structure.

FzN F Tris(difluoroamino)fluoromethane (CF(NF is colorless both as aliquid and as a gas and is found to be relatively shock-insensitive.Impact sensitivity is determined at 50% firings at 50 kg. cm. using anOlin-Mathieson Liquid Test Apparatus based on adiabatic liquidcompression and handling samples (initially cooled with solid carbondioxide) under anhydrous conditions. It is stable in solution in CFCl at200 C. for at least 15 hours and as a gas can be stored in 'borosilicateglass vessels for months without evidence of decomposition. Its vaporpressure in mm. (P), when T is the absolute temperature in K., isapproximately expressed by the equation from which the boiling point atatmospheric pressure is calculated to be about +5 C. and the heat ofvaporization to be about 6.5 kcal./ mole. The density of the liquid at75 C. is about 1.9 g./cc. The infrared absorption spectrogram shows astrong sharp peak at 7.8 microns corresponding to the CF group and astrong broad complex series of three major peaks between 10 and 11microns corresponding to the NF groups.

Analysis.Calculated for CF7N3I 6.4% C; 71.1% F; 22.5% N; mol. wt. 187.Found: 6.5% C; 71.8% F; 22.1% N; mol. wt. 183.

The oxidizing capacity was found to be 46.3 meq. of iodine per gram.

Nuclear magnetic resonance shielding values (usingchlorotrifluoromethane as the internal standard) at 23.8 (relativeintensity of 6+; corresponding to F-N bond) and at +138.7 (correspondingto FC bonds) show the pressence of 6 FN bonds for each FC bond. This isonly possible in the structure C FgN \F and is the highest such ratioknown for any organic compound.

Example 3 Weak absorption4.60; 14.47: unassigned Moderateabsorption-8.62 (CF), 9.55 (unassigned);

10.14 (N-F) 13.21, 13.90 (unassigned) Strong absorption-5.86 (C=N), 7.75(C-F) Very strong absorption-40.61; 11.23 (both N-F) Three nuclearmagnetic resonance shielding values are observed corresponding to thethree types of bound fluorine atoms:

Structural Relative Position Assignment Intensity 42. 24 -NF2 2. 0 +21.24 NF I. 0 +83. 04: EC-F 0. 8

These are thus in the simple ratio of 2: 1 :1 and since each F N groupincludes two Fs of the first type it follows that 1 3 the structureincludes one each of NF =NF and CF and is unambiguously Very weak-4.13(nearly symmetrical C=N) Weak9.46 (NF), 12.78 (unassigned) Moderate14.19(unassigned) Strong10.10, 10.66 (both NF) Very strong11.03 (NF) Threenuclear magnetic resonance shielding values corresponding to thedifferent types of fluorine bonds are observed:

Position Structural Relative Assignment Intensity 20 =N-F 1 42 NF2 2 -47NF:| 2

The different F N groups are ascribed to the two NF groups beingsomewhat unlike. It is apparent from these data that the structure isunequivocally FZN Example 4 This example illustrates the process of theinvention in which the poly(carbonylguanidylene)-ammeline mixture issuspended in a fluorine-inert liquid for fluorination.

A suspension of 750 mgm. of the mixture in 50 ml. of perfluoro octane (amixture of perfluorinated C isomers) is placed in a monel metal flaskhaving standard taper connections and fitted with an inlet for gas froma mixing manifold, a thermocouple and a vent line passing to a monelmetal condenser. All leads through which fluorine gas is to pass areconstructed of monel metal and a polytrifluoromonchloroethylenerotameter tube with a monel metal ball is employed to gauge the rate offlow. Nitrogen is passed through the suspension for a few minutes toflush oxygen from the system and fluorine is gradually introduced intothe stream and the nitrogen concentration decreased during 0.5 houruntil undiluted fluorine is passing through the suspension. Thisprocedure is reversed after about 2.6 hours toward the end of thereaction to decrease the concentration of fluorine to zero so that atotal of about 22.5 g. of fluorine has been passed through thesuspension. The temperature is maintained at about 28 to 30 C. Afterflushing with nitrogen, the suspension is filtered through a sinteredglass filter and a small amount of partially fluorinatedguanidine-urethane polymer is recovered. The filtrate is evaporatedcarefully in vacuo to give an amorphous grease-like hyperfiuorinatedproduct which, on analysis, is found to contain 48.5 percent F. and tohave an oxidizing capacity of 19.7 meq. of iodine per gram. The impactsensitivity is less than 70 kg. cm. It is' apparent that some of themore volatile products such as those described in Example 2 above areentrained and codistilled during evaporation of the perfluoro octanesolvent since after distillation this recovered solvent is found topossess an oxidizing capacity not found before use. The presence of suchproducts is also demonstrable by vapor phase chromatography.

When the above procedure is repeated at a reaction temperature of about47 to 35 C. and using larger amounts of fluorine at lower concentrationfor a longer time it is found that a greater amount of incompletelyfluorinated insoluble solid is recovered and the amorphous greasyhyperfluorinated product is more shock-sensitive with somewhat higheroxidizing capacity.

Example 5 A poly(carbonylguanidylene)-ammeline mixture is prepared byheating 18 g. of guanidine carbonate and 12 g. of urea (equimolaramounts) at to C. for 2.5 hours until evolution of gases (particularlyammonia) has ceased. The reaction mixture is then dissolved in an excessof 10 percent by weight aqueous sodium hydroxide and the polymerreprecipitated by carbonation with an excess of carbon dioxide to a pHof about 10. The product is collected, washed thoroughly with water anddried at 100 C. for 18 hours. It is very similar in its properties tothe product obtained in Example 1 above. Inherent viscosity is 0.158 intrifluoroacetic acid.

Analysis.-27.7% C.; 3.9% H.; 52.4% N.

Example 6 The procedure of Example 3 is employed using the product ofExample 4, under somewhat altered conditions. One gram of the mixture issuspended in 35 ml. of monofluorotrichloromethane at -56 C. and the gasstream is gradually enriched to 67 percent by volume of fluorine andmaintained at that point so that during 1.5 hours about 15 g. offluorine are passed into the suspension. The temperature rises to -33 C.due to the exathermic reaction. The reaction mixture is worked up asbefore to give solid incompletely fluorinated polymer and an amorphousgreasy hyperfluorinated product having an impact sensitivity of lessthan 8 kg. cm., an oxidizing capacity of 19.4 meq. of iodine per gramand containing about 32.9 percent by weight of fluorine on analysis.

Example 7 Fluorination of ammeline (2-hydroxy-4,6-diamino-striazine) iseffected in a manner similar to that described in Example 1.

In a 1.5 1. copper vessel of cylindrical shape immersed in a coolingbath at 16 C. is placed a copper tray containing 1.5 grams (0.012 mole)of previously thoroughly dried ammeline, the reactor is closed, flushedwith nitrogen and a stream of 5.5% by volume of fluorine is passedthrough the reactor at a rate of about 0.02 mole of fluorine per hour.The temperature is maintained at about 16 C. throughout 7 hours (a totalof 0.13 mole F the fluorine is discontinued and the cooling bath isallowed to warm to room temperature during 2 hours while the volatileproducts are flushed through with nitrogen and collected in a trapcooled in liquid air after removal of hydrogen fluoride by passage oversolid sodium fluoride maintained at 25 C. The condensate is distilled toobtain a fraction having a vapor pressure equal or less than 40 mm. ofHg at 75 C. and greater than 25 mm. of Hg at +25 C. A small fraction hasa higher boiling point. The main fraction is chromatographed asdescribed hereinabove and contains bis(difluoroamino) difluoromethane,tris(difluoroamino)fluoromethane, perfluoroformamidine andperfluoroguanidine in the approximate ratio (by moles) of 10:7.5:1:3.The exact ratios of formation of these products and the total yield arerather variable even in runs which are intended to be identical since itis impracticable to control every possible variable.

Example 8 The procedure of Example 7 is repeated employing 2.5 grams(0.019 mole) of dried ammeline with the fluorine stream containing 5.5%by volume of fluorine for 1.5 hours and 0.1% fluorine for 6.5 hours andmaintaining the outside of the reactor at 22" to 23 C. The fraction ofproduct boiling between 75" C. and +25 C. (at atmospheric pressure) isseparated, diluted with nitrogen so that it can be handled as a gas,passed through a scrubber containing 50 ml. of by weight aqueous sodiumhydroxide and the gases dried with calcium sulfate (hernihydrate) andcollected in a trap cooled with liquid air. Vapor phase chromatographyenables the separation of CF (NF and CF(NF in a ratio of about 2:1.

Example 9 The procedure of Example 8 is repeated employing as the sourcematerial an intimate mixture of 1.5 grams (0.012 mole) of dried ammelineand 0.5 gram (0.012 mole) of anhydrous sodium fluoride. The outside ofthe reactor is maintained at 18" C. The fluorine stream is 5.5% for 1.5hours and 9.1% by volume fluorine for a further 4.0 hours. Thetemperature inside the reactor is found to be about -7 to ;+5 C. part ofwhich is a result of the heat of reaction. A total of 0.106 mole offluorine is employed. The product is separated as above. The compound,CF (NF predominates.

Example 10* Ammeline trihydrofluoride is prepared by passing anhydrousgaseous HF over ammeline in a copper boat in a black iron tube untilthere is an increase in weight of 34%.

Analysis.-Calculated for: C N H O-3HF 16.0 meq./ gram F. Found: 15.3meq./gram H+; 15.6 meq./gram F.

In a copper U-tube (100 ml. capacity) in an ice bath are placed 1.6grams (0.009- mole) of the above ammeline trihydrofluoride and a streamof fluorine in nitrogen is introduced (after initially flushing withnitrogen). For two hours the stream contains 9.2% by volume fluorine andfor a further two hours it contains 7.3% F The temperature in thereactor reaches 17 C. during some parts of the reaction. A total of0.099 mole of F is employed. The product is separated as above toprovide a fraction from which CF (NF and CF(NF perfluoroformamidine andperfluoroguanidine are separated as above. The product boiling above 25C. is obtained in almost equal amount to the total of the above.

Example 11 Ammeline trihydrofluoride (1.5 grams; 0.08 mole) isfiuorinated in the apparatus and by the procedure of Example 9 coolingthe reactor at C. and using first 5.5% fluorine for 1.5 hours and the9.1% fluorine for 4.8 hours. A total of 0.125 mole of F is used.Products are worked up and found to contain particularly CF (NF It willbe noted that a higher proportion of total fluorine was employed than inExample 10.

Example 12 In the apparatus of Example 10 are placed 1.7 grams (0.013mole) of thoroughly dried ammelide (2,4-dihydroxy-6-amino-s-triazine)and, after the usual preliminary flushing with nitrogen, a stream offluorine in nitrogen (5.2% to 7.6% by volume) is passed over theammelide at C. for 7.4 hours. The volatile products (boiling below 25mm. at 25 C.) includes CF (NF and CF (NF In addition there is aconsiderable amount of solid amorphous product with an impactsensitivity less than 100 kg. cm. and with an oxidative capacity of 13.9meq. of iodine per gram. Analysis shows 21.0% C; 27.1% F; 31.0% N.

Example 13 Melamine (1.20 grams; 2,4,6-triamino-s-triazine) isfiuorinated in the apparatus of Example 7 after grinding to a finepowder and drying at 100 C. and 0.1 mm. Hg pressure for 16 hours. Duringthe reaction the temperature (external) and concentration of fluorineare increased as shown in the following table.

The amorphous product remaining in the reactor is yellow, free-flowingand oxidizes iodide ion. The volatile components are separated as aboveto give fractions as follows:

(1) Boiling l78 C./0.1 mm. Hg to --78 C./44 mm. Hg.

(2) Boiling '-78 C./44 mm. Hg to +25 C./50 mm. Hg.

(3) Boiling above 25 C./50 mm. Hg.

Fraction 2 contains compounds CF (NF and CF (NF which are isolated bygas chromatography as described above. This fraction also contains smallamounts of perfluoroformamidine and perfluoroguanidine.

Fraction 3 was divided by chromatography into several subfractions. Oneof these possessed, among others, nuclear magnetic resonance peaks at+101 and i+87.2 to +83.8 which are assigned to the groupings --NFCF NFand NFCF NFCF' in the compound FgNC FQNF C FzNF C F-NFg Anothersubfraction showed several peaks including one at +101, assigned to NFCFNF as occurs in the compound Repeating the above procedure usingmelamine intimately mixed with sodium fluoride and with melaminetrihydrofluoride and with different concentrations of fluorine alsoresults in the formation of volatile products from which CF (NF and CF(NF are isolated.

Example 14 The fluorination procedure described above is repeatedemploying 2.8 grams of dry potassium cyamelurate as the source materialwith 10% F at 25 C. and the compounds CF (NF CF(NF perfiuoroguanidine,perfiuoroformamidine, and other materials are obtained.

Example 15 Guanidine hydrochloride (0.74 gram; 0.008 mole) isfiuorinated in the U-tube reactor of Example 10 cooled at 270 C. using0.062 mole of F (at concentrations of 7.4% to 13.1% over two hours). Theheat of reaction raises the internal temperature to 0 C. The reactionmixture is found to contain the compounds CF (NF and CF (NF as well asperfluoroformamidine and apparently some perfluoroguanidine.

Example 16 Dicyanamidazide (NEC-N=C(N )NH and its hydrofiuoride arelikewise fiuorinated (at 25 C. with 4% fluorine for 1.3 hours and at +25C. with 10% fluorine for 1.5 hours, respectively) to produce compoundsCF (NF and CF(NF The other products may be present as well.

Example 17 A mixture of 1.5 grams (0.012 mole) of dry ammeline and 75ml. of perfluorotributylamine is placed in a 10 inch long copper tube 1inch in diameter closed at the lower end, with a reflux condenser andtakeoff at the top and with a monel metal dispersion disk connected to aconduit for in-gases at the bottom. After flushing with 17 nitrogen,fluorine in nitrogen is bubbled through the mixture the concentrationbeing increased from 5.7 to 53% over 15 minutes and then maintained at53% for 90 minutes so that a total of 0.5 mole of fluorine is employed.The oil-gases, after passing through a sodium fluoride tube at 25 C. arepassed through a Pyrex trap cooled in liquid air in which the volatileproducts of the reaction collect. During the fluorination reaction themixture in the tube reaches about 38 C, The condensate in the liquid airtrap is fractionated as in the above examples and from the middlefraction (boiling from about 40 mm./75 C. to 20 mm./ 25 C. it ispossible to obtain perfluoroformamidine, perfluoroguanidine,bis(difluoramino)-difluoromethane and tris(difluoramino fluoromethane.

Example 18 The apparatus of Example 17 is charged with a mixture of 1.5g. (0.012 mole) of ammeline and 6 grams of graphite as diluent. Noliquid is used and the process provides a substantially fluidized bed.The solids are maintained in suspension by a flow of 0.013 cu. ft./min.of N Florine is introduced into the gas stream at 1.8% for one hour andat 6.0% for a further two hours so that a total of 0.19 mole isemployed. The temperature of the mixture is maintained between -35 and22 C. The off-gases pass through sodium fluoride at 100 C. and arecondensed and finally worked up as above. Somewhat higher yields ofperfluoroformamidine and perfluoroguanidine are obtained than in Example17 above, as well as CF (NF and CF(NF EXAMPLE 19 Position StructuralApproximate of peak assignment relative areas 23. 5 NFg 4 +66. 4 -CF3 3+89. 44 NF 1 +131. 24 -CF 1 From these positions and area ratios of thepeaks it follows that the structure of the compound is:

Because of their high oxidizing capacities the hyperfiuorinated productsof the invention are useful in propellant compositions when combinedwith fuels such as lithium and boron and with an additional oxidizersuch as ammonium perchlorate to consume any carbon which is present,such as that in the hyperfluorinated oxidizer as well as in any organicbinder which is used.

What is claimed is:

1. A fluorinated oxidant compound selected from the and =C= radicals; Zis a member of the group consisting of F, -CF2NF2, -CF=NF2,

i-NF5 and CF(NF radicals; n is an integer from zero to one; R is adivalent radical only when Y is a linking radical of the groupconsisting of =C= and and n is zero when Y is =C=.

2. The compound having the formula /NF, FN=C 3. The compound having theformula FN=CNF1 4. Tris(difluoroamino)fluoromethane having the formulaCF (NF References Cited Maxwell et al.: Jour. Amer. Chem. Soc," vol. 80,pp. 548-9 (1958).

ROBERT V. HAINES, Primary Examiner.

US. Cl. X.R.

@233 UNITED STATES PATENT OFFICE CERTIFICATE OF CORREQTION Patent: No.EJ614162 Datod August l2, l 959 Invontorh) Robert J. Koshar and DonaldR. Husted It 1: certifiod that error appurl in the above-identifiedpatant and that aid Letter: Pntont are horoby correct an about: below:

r, In column 1 line 35, "exathermic" should read ----exotherm1c-- Incolumn 15, line 2, "0.1%" should read --9.l%-- In column 16, line 53,"-270: C." should read -27 C.-- In column 17, line 48, "-NF" should read;NF--

and in line 49, "-CF" should read E-CF In column 18', lines 20-25 shouldalso include =CII- SIGNED -KND SEALED SEAL) 1mm:

Edward M. Flew-her. Ir. E: m Am: ting Officcr mifllionor or PM

1. A FLUORINATED OXIDANT COMPOUND SELECTED FROM THE GROUP OF COMPOUNDSHAVING THE FORMULA: